A liquid crystal display (LCD) is a kind of flat panel display (FPD) which displays images by the property of the liquid crystal material. In comparison with other display devices, the LCD has the advantages in lightweight, compactness, low driving voltage and low power consumption, and thus has already become the mainstream product in the whole consumer market. However, the liquid crystal material of the LCD cannot emit light by itself, and must depend upon an external light source. Thus, the LCD further has a backlight module to provide the needed light source.
Generally speaking, backlight modules have been developed based on size requirements into a type of edge lighting structures and another type of bottom lighting structures, which are categorized by locations of lamp tubes thereof. A light source of the type of edge lighting structures is a single light source placed aside, and a light source of the type of bottom lighting structures is placed right beneath. The lamp tubes of the backlight modules must be featured with high brightness and a long lifespan, etc. They currently include cold cathode fluorescent lamps (CCFL), hot cathode fluorescent lamps, light emitting diodes (LED) and electroluminescence (EL), etc.
Among them, the CCFL has characters of high luminance, high efficiency, a long lifespan, and high color rendering, etc. Besides, it is much easier to be assembled with light reflection components to form a thin-sheet lighting device due to its cylinder shape. Therefore, using the CCFL as main backlight sources was once a main trend for making backlight modules. However, the CCFL is gradually eliminated by the present trend of soaring environmental awareness today due to its filled content of mercury vapors. Since using LED as backlight sources has an advantage of energy saving and environmental protection over the CCFL, it becomes a trend in backlight development to replace the CCFL by the LED. A lighting structure of the LED is generally called as a light bar in practice.
Referring to FIG. 1, a front view showing a structure of a currently existing LED light bar is illustrated in FIG. 1. As shown in FIG. 1, an LED light bar structure 90 comprises a circuit board 91 of a substantially long strap shape and a plurality of LEDs 92. The LEDs 92 are arranged on an upper surface of the circuit board 91 and fixed thereon through a plurality of solder points (not shown) to be electrically connected with the circuit board 91. The LEDs 92 of the light bar structure 90 emit lights toward a side edge of a light guide plate (not shown), and then emit lights toward a top surface of the light guide plate by special reflection of the light guide plate, so it can be directly installed to an original location of the CCFL to replace illumination of the CCFL. Although using LEDs as the backlight source has advantages of lightness and thinness, environmental protection, electricity saving, and so on, the aforementioned existing LED light bar still has a few problems.
The white light LED is usually achieved by a means of optical mixing. For example: using a blue LED to activate a yellow fluorescent body; using an ultraviolet LED to activate a RGB (red, green, blue) fluorescent body; or using red, green and blue LEDs to achieve a white by adjust the brightness thereof, respectively. However, because of the reasons that has different manufacturing condition and are difficult to control, such the mixed LED by above-mention means has a phenomenon of chromaticity difference. When a backlight module is in design, the general method is alternate to mix the LEDs, so as to achieve a white light.
Referring to FIG. 2, a front view showing a structure of another currently existing LED light bar is illustrated in FIG. 2. As shown in FIG. 2, an LED light bar structure 80 comprises a circuit board 81 of a substantially long strap shape. A plurality of first LEDs 82 and a plurality of second LEDs 83 are alternately disposed on the circuit board 81. Each of the first LEDs 82 has the same chromaticity, and each of the second LEDs 83 also has the same chromaticity. Besides, the chromaticity of the first LEDs 82 and the chromaticity of the second LEDs 83 can mix as a white light.
However, by the traditional means to achieve a uniform mixed white color, it is necessary to confirm that the chromaticities of the selected first LEDs 82 are complete identity, and the chromaticities of the second LEDs 83 are also complete identity and accurately coordinate with the chromaticities of the first LEDs 82. Otherwise, the backlight module will appear a phenomenon of “Mura”. Thus, the material selection of the LEDs is too exacting, so that it causes a waste of the material, and it is difficult to control the identical chromaticity between the different backlight modules.
As a result, it is necessary to provide an LED light bar structure to solve the problems existing in the conventional technologies.